JP2001223572A - Output circuit with current restriction function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current restriction function which can reduce an output current restriction value even in an overcurrent state due to the shorting of an output terminal and the abnormality of a load and to protect a circuit element from overcurrent in an output circuit applied to a regulator circuit and a high side driver circuit. SOLUTION: In an output circuit B1, a current mirror circuit 3 forms mirror currents I1 and N.I1 from a power source 11, and supplies current I1 to a current control circuit 5 and current N.I1 to an output terminal. A current control circuit 4 has a control element Q3 and a current source 14 and controls current Ia flowing in the current source 14. A boltage control circuit 4 controls output voltage by a control element Q2 driven by a voltage source 12 and is connected between the output terminal and the current power source 14. When output voltage becomes lower than voltage source 12, the control element Q2 is turned off and current I2 is interrupted. Even if output becomes an overcurrent state, output current is restricted to N.Ia.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output circuit having a current limiting function applicable to a high-side driver circuit and a series regulator circuit, and more particularly to a method for suppressing a current value flowing through a load in an overcurrent state due to a load abnormality. And an output circuit with a current limiting function.

[0002]

2. Description of the Related Art Conventionally, regulator circuits, output circuits, etc.
The output control circuit, which controls the output in various ways, protects the load and output lines connected to these devices from overcurrent when an overcurrent occurs due to a ground fault at the output terminal or an abnormal load. A limiting function and an overcurrent detection function are provided.

Therefore, a power supply V which has been conventionally used is
In the output circuit or a regulator circuit to output a DC output voltage V _o from cc, it describes an example having these functions. Figure 1 shows an example of an output circuit for outputting the DC output voltage V _o from the power source Vcc. Transistor Q ₁ is connected between a power supply Vcc and an output terminal, the transistor Q ₁ is are adjusted so that the output voltage V _o at the output terminal is output.
Then, the driving circuit of the transistor Q ₁ is, the resistance R _2, a resistor R ₃ and the transistor Q ₃ is formed in the base of the transistor Q ₁ is connected to a connection point of the resistor R ₂ and the resistor R ₃ . The base of the transistor Q _3, is connected to a connection point between the resistor R ₄ resistor R _5, the input voltage V _i is applied is divided with resistance R ₄ in the resistor R _5.

The output circuit A1 having such a circuit configuration is
Become a high-side driver. In this output circuit A1
And the input voltage V_iIs not supplied, the
Star Q _ThreeIs turned off and the transistor Q₁Is not driven
Therefore, at the output terminal, the output voltage V_oBecomes 0 potential,
Output current I_oDoes not flow. Input voltage V_iIs supplied
And the transistor Q_ThreeIs turned on and the transistor Q
₁Is driven on. Resistance R_TwoAnd resistance R_ThreeBy
The transistor Q according to the ass voltage₁Is controlled,
Output voltage V_oIs output, and the output current I_oFlows.

In the output circuit A1, a load abnormality or the like occurs.
A current limiting circuit 1 is added to prevent overcurrent
ing. This current limiting circuit 1 includes a transistor Q_TwoBut
Anti-R _TwoConnected in parallel to_TwoBase of
Is the power supply Vcc and transistor Q ₁Resistance inserted between
Anti-R₁Is biased by the voltage between both ends of the resistor R.₁Is output
Current I_oCurrent detection.

[0006] Therefore, when the output current I _o is within a predetermined range, the voltage across the resistor R ₁ is small, the transistor Q ₂ is not conductive, the driving circuit of the transistor Q ₁ is continuously conducting transistor Q ₁ . However, the output current I _o increases, the voltage across the resistor R ₁ increases,
The conductivity of the transistor Q ₂ will change to linear. Then, since the base bias of the transistor Q ₁ is changed, the output current is controlled to be constant _{I o = V BE (Q 2} ) / R 1. Thus, by providing the current limiting circuit 1 by the transistor Q _2, thereby preventing an overcurrent from flowing to the load.

[0007] In the output circuit A1 includes a current limiting circuit 1 shown in FIG. 1, the current limiting circuit 1, it has realized a resistor R ₁ and the transistor Q _2, is made in a simple circuit configuration. However, here, the current limit value I _omax of the output current I _o
Looking for the base-emitter voltage of the transistor Q ₂ as V _BE, the current limit value I _omax will be determined by the _{I omax = V BE / R 1} . Generally, a transistor is easily affected by temperature, and the temperature fluctuation of the base-emitter voltage V _BE is as large as about −2 mV / ° C. According to this equation, the current limit value _Iomax also fluctuates greatly according to the temperature fluctuation.

The current limit value I_omaxTo increase the accuracy of
For this purpose, as shown in FIG. 2, a differential amplifier AMP1 was used.
There is a current limiting circuit 2. In FIG. 2, the output circuit A1
The circuit configuration is the same as that of FIG.
showed that. Therefore, as the current limiting circuit 2, the resistor R₁When
Transistor Q _TwoIn addition, the differential amplifier AMP1 and the reference
Source V_RHas been added.

In the output circuit A1 shown in FIG. 1, a change in the base-emitter voltage V _BE caused by a temperature change is caused by the current limit value I _omax.
The output circuit A of FIG.
In 1, the differential amplifier AMP1, is adapted to compare the voltage across the resistor R ₁ and the reference voltage V _R. For this reason, the transistor Q ₂ base-emitter voltage V
Even under the influence of _BE is temperature fluctuation, the transistor Q ₂ is driven by the differential amplifier AMP1, no effect on the current limit value I _omax, can improve the accuracy.

Further, a circuit example in which the current limiting circuit 2 provided in the output circuit A1 shown in FIG. 2 is applied to the series regulator circuit A2 to _improve the accuracy of the current limiting value _Iomax is shown in FIG.
It was shown to. The series regulator circuit A2 is connected to the transistor Q ₁ between the power supply Vcc and the capacitor C _1, by controlling the transistor Q _1, and outputs an output voltage V _o through the capacitor C _1. Connected to the capacitor C ₁ and a resistor R ₁₁ in parallel a resistor R _12, the voltage across the capacitor C _1, i.e., it detects the output voltage V _o. Then, the differential amplifier AMP2 is, compared with the resistor R ₁₁ and the resistor R ₁₂ Metropolitan output voltage V _o is detected from the reference voltage V _REF,
Controls the transistor Q ₁ on the basis of the comparison result.
By such a circuit configuration, the series regulator circuit A2 outputs a constant voltage V _o.

Here, when the current limit value I _omax in the series regulator circuit A2 is _obtained , it is found that I _omax = V _R / R _{1 and} is not affected by temperature fluctuation. Then, the output voltage V _o is a _{V o = V REF (R 11} + R 12) / R 12, since V _REF is constant, the output voltage V _o is also a constant voltage.

Such a series regulator circuit A2
Since the current limiting circuit 2 is provided, the accuracy of the current limiting value can be improved, similarly to the output circuit A1 of FIG.

[0013]

[SUMMARY OF THE INVENTION However, when these output circuits A1 or series regulator to the resistance R ₁ of the current limiting circuit connected to the circuit A2 having a high-precision resistor, further higher precision current limit can be achieved, the differential control circuit of the transistor Q ₂ is the amplifier aMP
1 has a disadvantage that oscillation is easy in the current limiting circuit, a circuit must be separately prepared for the countermeasure, and the circuit is complicated.

Accordingly, the present invention provides an output circuit having a current limiting function in a high-side driver circuit or a series regulator circuit, which can be used when an overcurrent state occurs.
It is an object of the present invention to protect circuit elements and to improve the accuracy of a current limit value.

[0015]

In order to solve the above-mentioned problems, an output circuit having a current limiting function applicable to a high-side driver circuit and a series regulator circuit comprises a current mirror circuit, a current control circuit and a voltage control circuit. The current mirror circuit forms a first current and a second current having a mirror ratio of 1: N based on a current from a power supply, supplies the second current to an output terminal, and the current control circuit includes: A first current control element and a first current source;
A current control element controls the first current flowing to the current source, and the voltage control circuit is driven by a first voltage source and connected by a voltage control element connected between the output terminal and the first current source. Control the output voltage. Then, when the output voltage becomes higher than the voltage of the first voltage source, the voltage control element operates to control the first current flowing through the first current control element, so that the load current is reduced. When the amount is small, the second current, that is, the output current is reduced, so that the output current can be limited.

Further, in order to stop the operation of the current mirror circuit, the current of the first current source is cut off or an output cut circuit for stopping the first current is connected to lower the output voltage. I made it. The voltage / current conversion circuit is connected to the output terminal, and the second current source is controlled so that the current limit value decreases as the output voltage decreases due to overcurrent or the like.

A third current source connected in parallel to the first current source and a short control circuit including a second current control element for controlling the third current source are connected, and the third current source is connected to the third current source in accordance with the output voltage. The current of the third current source is output, and when the output voltage drops to a predetermined voltage, the current of the third current source is cut off by the second current control element. The value was reduced.

Further, by detecting the rise of the power supply voltage or the rise of the current mirror circuit and interrupting the current of the third current source after a lapse of a predetermined time,
The output voltage rises faster.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
Each embodiment will be described with reference to FIGS. [First Embodiment] FIG. 4 shows an output circuit B1 according to a first embodiment. The output circuit B1 includes a current mirror circuit 3, a voltage control circuit 4, and a current control circuit 5 as basic circuit configurations, and a voltage Vcc supplied from a power supply 11 is a constant voltage Vcc.
to output the result as _o, the output circuit B1 can be used as a voltage regulator circuit and the high-side driver circuit.

The current mirror circuit 3 has a PNP transistor
Star Q_1aAnd PNP transistor Q _1bConsists of a voltage
It is connected to the power supply 11 of Vcc. And the mirror ratio is
1: N, the transistor Q_1aFlow
Current I₁Then, the transistor Q_1bHas NI₁
Current flows. Transistor Q_1bIs the output terminal
Connected to child.

The voltage control circuit 4 includes a PNP transistor Q
₂ and _a voltage source 12 of _a voltage Va, and _a transistor Q ₂
Is connected to the collector and output terminal of the transistor _Q1b . The base of transistor Q ₂ is biased with voltage V _a. The current control circuit 5 includes an NPN transistor Q ₃ , a voltage source 13 for the voltage _Vb , and _a current source 14 for the current _Ia.
In the configuration, the collector of the transistor Q ₃ is connected to the collector of the transistor Q _1a. The base of transistor Q ₃ are biased by a voltage V _b, and the current source 14
The, the current I _a flows a current I ₂ flowing in the current I ₁ and the transistor Q ₂ to which flows through the transistor Q ₃ is connected to monkey synthesis.

In the current control circuit 5 shown in FIG.
FIG. 5 shows a specific circuit example of the current source 14. Transis
TA Q_ThreeResistor R_aConnect. This resistance R_a
Current I flowing through_aIs set to a constant current, the voltage source 13
Is constant voltage V_b1And it is sufficient. Output configured in this way
In the circuit B1, the transistor Q_TwoBase Emi
Voltage between terminals_BEThen, the output voltage V_oIs V_o= V_BE+ V_a Becomes Voltage V of voltage source 12_aBy changing
Force voltage V_oCan be controlled. In addition, the current control circuit
Current I which is the output current of path 5₁Is I₁= I_a-I_Two And the transistor Q_TwoCurrent I flowing through_TwoIs the output power
Flow I_oThen I_Two= N × I₁-I_o So I₁= (I_a+ I_o) / (N + 1). Therefore, the output current I_oIs the largest
Therefore, the output terminal of the output circuit B1 is
Assume that it is grounded. Then, the transistor Q _TwoHa
And the current I_TwoWill not flow. Therefore, the maximum
Becomes I_Two= 0, that is, the transistor Q_1b
Current NI flowing through₁Is when everything flows to the load
Therefore, the current limit value I_omaxIs given by I_omax= N × I_a Becomes

With the circuit configuration shown in FIG. 4, even if the load is short-circuited to the ground and an overcurrent occurs,
The maximum current flowing can be suppressed to the current limit value _Iomax . Further, the output circuit B1, since the flow to connect the current I ₂ flowing through the transistor Q ₂ to the current source 14 of the current control circuit 5, when the output current I _o is small, consumes reduces the current of the current mirror The current can be reduced.

[0024] In addition, changing the current I _a of the current source 14,
The magnitude of the maximum output current _Iomax can be adjusted. When an abnormal current occurs in the load and an excessive current flows, the output current _Iomax can be adjusted.
_o can be suppressed to the current limit value I _omax . Next, FIG. 6 shows a case where the output circuit B1 shown in FIG. 4 is applied to a series regulator circuit B2. In FIG. 6, FIG.
The same reference numerals are given to the same parts as.

FIG. 4 also shows the series regulator circuit B2.
In the same manner as shown in FIG.
The circuit 4 and the current control circuit 5 have a basic circuit configuration, and an output terminal
Capacitor C₁Is connected and supplied from power supply 11.
Voltage Vcc to constant voltage V_oOutput as
You. The series regulator circuit B2 is shown in FIG.
The difference from the power circuit B1 is the voltage control circuit 5.
In the voltage control circuit 5 of the output circuit B1, the voltage source V_aBut tiger
Transistor Q_TwoConnected to the base of the
In the voltage control circuit 5 of the regulator circuit B2, the output voltage V
_oSo that the transistor Q has a predetermined voltage. _TwoControl
That is.

Specifically, the output voltage V_oThe output voltage setting
Resistance R₁₁And resistance R₁₂And the differential amplifier AMP1
And the reference voltage V of the voltage source 15_REFAnd
Be compared. According to the comparison result, the transistor Q_TwoBut
And outputs the set output voltage. This output voltage
V_oCorresponds to the series regulator circuit 30 shown in FIG.
As in the case, V_o= V_REF(R₁₁+ R₁₂) / R₁₂ Becomes The operation as seen from the current is the same as that of the output circuit B1 shown in FIG.
Similarly, the output current I _oCurrent limit value I for_omax
Is similarly determined.

Next, in the output circuit B1 shown in FIG. 4, the output cut circuit provided by stopping the operation of the constant current source of the current control circuit, for the case in which down the output voltage V _o, Figure 7 It will be described with reference to FIG. The output circuit B3 shown in FIG. 7 has a current mirror circuit 3, a voltage control circuit 4 and a current control circuit 5 as basic constituent circuits, and converts the voltage Vcc supplied from the power supply 11 into a constant voltage V Output as _o . 7, the same parts as those in FIG. 4 are denoted by the same reference numerals.

In the output circuit B3, an output cut circuit 6 is inserted between the current control circuit 5 shown in FIG. 4 and the ground.
The output cut circuit 6, an output cut switch SW _{1 in} which is controlled by the input voltage V _i provided, the switch S
W ₁ is connected between ground and the current source 14 of the current control circuit 5. To output cut, turning off the switch SW ₁ at the input voltage V _i, the current I _a of the current source 14 does not flow. Then, the transistor Q ₃ current I ₁ stops flowing, and because of course does not flow even current I ₁ of transistor Q _1a, the current N of the transistor Q _1b in mirror relationship
· I ₁ is also stopped. Therefore, the output voltage Vo _decreases .

FIG. 8 shows an output circuit B3 having a specific circuit configuration for the voltage control circuit 4 and the output cut circuit 6 shown in FIG. In the figure, the same parts as those in FIG. 7 are denoted by the same reference numerals. In Figure 8, that shown a specific circuit configuration, the voltage source 12 of the voltage control circuit 4, a switch SW ₁ and a driving portion of the output cut circuit 6.

Looking at the voltage control circuit 4, the transistor Q
Voltage source for supplying the _second base voltage V _a 12, the resistance R
₂₁ , a PNP transistor Q ₂₁ and a current source 16. The emitter of the transistor Q ₂₁ is connected to the power source 11 through a resistor R _21, a voltage Vcc is supplied. The collector is grounded via the current source 16.
The base of transistor Q ₂₁ is connected to the base of the transistor Q _2.

Looking at the output cut circuit 6, the output power
NPN transistor Q that functions as a switch for power_Four
Whose collector is the current source 1 of the current control circuit 5.
4 and their emitters are connected to ground, respectively.
You. Further, the transistor Q _FourThe base of the resistor R₆₁
And resistance R₆₂Input voltage V divided by_iIs applied. What
In FIG. 8, the current source 14 has the same configuration as that shown in FIG.
And the resistor R_aIs used.

Therefore, the input to the output cut circuit 6 is
Force voltage V_iIs H, the transistor Q_FourIs on
Transistor Q_FourThrough the current I_aFlows. so
Then, the current I₁And current I_TwoSo that it can also flow
become. In this case, the operation of the output circuit B3 is shown in FIG.
This is the same as the output circuit B1. At this time, the current source 16
The flowing current is I_{twenty one}And the transistor Q_{twenty one}Base of
Emitter voltage is V_BE(Q_{twenty one}), The voltage source 12
Voltage V_aIs V_a= Vcc-R_{twenty one}× I_{twenty one}-V_BE(Q_{twenty one}). Output voltage V of output circuit B3_oIs the transistor
Q_TwoThe base-emitter voltage of V_BE(Q_Two)
And V_o= V_a+ V_BE(Q_Two). For example, the output circuit B3 is provided in the same semiconductor chip.
When forming in an integrated manner, V_BE(Q_Two) ≒ V
_BE(Q_{twenty one}), As a result, the output voltage V_oIs V_o= Vcc-R_{twenty one}× I_{twenty one} Becomes This is the current I of the current source 16_{twenty one}Variable
Output voltage V_oCan be changed, and
Transistor Q_TwoBase-emitter voltage V_BE(Q _Two)
Is the transistor Q_{twenty one}Base-emitter voltage V
_BE(Q_{twenty one}), The output voltage V_oIs the base
Being independent of the emitter-to-emitter voltage and affected by temperature fluctuations
Absent.

On the other hand, the input voltage V _i which is input to the output cut circuit 6 when the L, the transistor Q ₄ is turned off, and disconnects the current I _a from the current source 14. Then, the current I ₁ and the current I ₂ cannot flow, and
The output circuit B3 stops functioning as a regulator, the output voltage Vo _drops , and the output terminal goes to the ground potential via the load.

As described above, the output circuit B3 shown in FIG.
Then, the output cut circuit 6 is connected to the current source 14 and
Style I_aTo stop the operation of the output circuit B3,
FIG. 9 shows the operation of the current mirror circuit 3 of the output circuit 30.
Operation is stopped and the output voltage V _oTo bring down
The basic circuit configuration is shown below. In the figure, the basic circuit configuration of FIG.
The same parts as those shown in FIG.

In the output circuit B4 shown in FIG. 9, the output cut circuit 6 shown in FIG. 7 is connected to the current mirror circuit 3, and the other circuit configuration is the same as the output circuit B shown in FIG.
3 is the same as the circuit configuration of FIG. So that in parallel with the transistor Q _1a to form a current mirror circuit 3, connecting the switch SW ₁ of the output cut circuit 6 to the base and emitter of the transistor Q _1a.

Here, the input voltage V _i of the output cut circuit 6
By, but turning on or off the switch SW _1, when the switch SW ₁ is turned off, the output circuit B4 is the same operation as the output circuit B3 shown in FIG. 7, and outputs an output voltage V _o. On the other hand, when the switch SW ₁ is turned on, shorting the base and emitter of the transistor Q _1a, furthermore,
The base of the transistor _Q1b is set to the power supply voltage Vcc. Therefore, the transistor Q _1b is turned off, and the flow of the current N · I ₁ is stopped. As a result, the output voltage V _o becomes down, the output terminal becomes the ground potential through the load.

FIG. 10 shows a specific circuit configuration of the output circuit B4 in FIG. The specific circuit configuration shown in FIG. 10 is the same as the output circuit B3 shown in FIG. 8, except that the output cut circuit 6 is not connected to the current source 14,
The difference is that the transistor Q _1a forming the current mirror circuit 3 is connected in parallel with the transistor Q _1a , and since the transistor Q _1a is connected to the Vcc side of the power supply 11,
The transistor Q ₄ is a switch SW _1, instead of the NPN transistors, it is used PNP transistor.

The input voltage V input to the output cut circuit 6
When _i to H, the transistor Q ₄ are turned off, in this case, the same operation as the output circuit B1 in FIG. 4, the output voltage V _o from the output terminal is output. On the other hand, when the input voltage V _i which is input to the output cut circuit 6 L, and the transistor Q ₄ are turned on. Therefore, as described in the operation of the output circuit of FIG. 9, it means to stop the operation of the current mirror circuit, bring down the output voltage V _o.

In FIG. 10, the voltage control circuit 4
8 is the same as the voltage control circuit 4 in the output circuit B3 shown in FIG. As described above, in the output circuit B4 shown in FIGS. 9 and 10, since the operation of the current mirror circuit is directly stopped by the output cut circuit 6, the leakage current or the like flowing through the transistor _Q1b at the time of high temperature becomes the output current. It does not flow as _Io .

As described above, the output circuit B1 according to the first embodiment
FIG. 11 shows the output voltage-load current characteristics of B4 to B4. The horizontal axis, the load current, i.e., shows the output current I _o, the vertical axis represents the output voltage V _o. The characteristics shown in the figure show the load characteristics of the output voltage V _o when the current is limited, and the characteristics are drooping at the current limit value I _omax .

According to the first embodiment described so far, the present invention can be applied to a high-side driver circuit or a series regulator circuit, and can constitute an output circuit having a current limiting function. When the output current _Io is small, the current of the current mirror circuit can be reduced to reduce current consumption. [Second Embodiment] In the output circuits B1 to B4 having a current limiting function according to the first embodiment, as shown in FIG. 11, the output voltage-load current characteristic has a drooping characteristic. However, this characteristic, even when the output voltage V _o is short-circuited to ground, the current limit value I _omax, I _omax = N × become current I _a flows. Therefore, even in the transistor Q _1b is output element, so that the I _omax flows. _Assuming that the power loss in the transistor Q _1b is P, P = Vcc ×
I _omax occurs. When the power supply voltage Vcc is high, the element itself generates a large amount of heat and may be thermally damaged.

Therefore, in the second embodiment, a voltage / current conversion circuit is provided in the output circuit shown in FIG.
In accordance with the output voltage V _o, and to vary the current value I _a current source 14. Even shorted output voltage V _o is, it is possible to reduce the current limit value I _omax. In FIG.
An output circuit in which a voltage / current conversion circuit is provided in the output circuit configuration shown in FIG. 4 is shown. The basic circuit configuration of the output circuit C1 shown in FIG. 12 is the same as that of the output circuit B1 of FIG. 4, and the same parts as those of FIG.

The voltage / current conversion circuit 7 has a variable current source 17 connected in parallel with the current source 14. Then, the current source 17 in accordance with the magnitude of the output voltage V _o, a current flows I _a2. In the output circuit B1 shown in FIG. 4, the current _Ia flows through the current source 14, but in the output circuit C1 shown in FIG.
The current _Ia is _{defined as Ia} = _Ia1 + _Ia2 , where the current of the current source 17 is _Ia2 .

[0044] Thus, when there is an output voltage V _o it is smaller than a predetermined value, by reducing the current I _a2, to reduce the current I _a. FIG. 13 shows a specific circuit configuration of the voltage / current conversion circuit 7 in the output circuit C1 shown in FIG.
The output circuit C1 itself can adopt the specific circuit configuration used in the first embodiment. FIG. 13 shows the case where the resistor _Ra1 is used for the current source 14.

The voltage / current conversion circuit 7 comprises NPN transistors Q _a1 and Q _a2 and a resistor R _a2.
a1 and the bases of the transistors _Qa2 are connected to each other to form a current mirror circuit. Here, the mirror ratio is set to 1: 1. By changing the mirror ratio, the detection sensitivity can be changed. Transistor Q _a1
Is connected to the resistor R _a1 , and the current I _{a
Divide a2} . The collector of one transistor _Qa2 is connected to the output terminal via a resistor _Ra2 . A mirror current _Ia2 flows through the resistor _Ra2 .

Next, the operation of the voltage / current conversion circuit 7 will be described. Usually, the magnitude of the output voltage V _o is controlled by the voltage control circuit 4. The output voltage V _o, as described above, is _{V o = V a + V BE} (Q 2). Here, transistor Q _a1 and transistor Q _a2
A mirror ratio of 1: Since the 1, current I _a2 becomes _{I a2 = (V o -V BE} (Q a2)) / R a2. On the other hand, the current I _a1 to flow through the current source 14, when the base-emitter voltage of the transistor Q ₃ and V _BE (Q _3), the _{I a1 = (V b -V BE} (Q 3)) / R a1 . These, when determining the current I _a, the _{I a = I a1 + I a2} = (V b -V BE (Q 3)) / R a1 + (V o -V BE (Q a2)) / R a2. Then, if the voltage source _Vb is a constant voltage source,
The current _Ia1 is constant and constant. When the output voltage V _o is changed, because changing the current flowing change the bias of the transistors Q _a2, current I _a2 even if the output voltage V _o
It changes according to the change of.

Therefore, as described above, since V _o = V _a + V _BE (Q ₂ ), the current limit value I _omax of the output circuit C2 is I _omax = N × I _a = N × (I _a1 + I _a2) = N × _{[(V b -V BE (Q 3} )) / R a1 + (V a + V BE (Q 2) -V BE (Q a2)) / R a2 ] and becomes. Here, when the output voltage V _o is short-circuited to the ground, when V _o <V _BE (Q _a2 ), the transistor Q _a2 is turned off and I _a2 = 0, so the short-circuit current I _short at that time is I _short = N × I _a = N × [(V _b −V _BE (Q ₃ )] / R _a1

FIG. 13 shows output voltage-load current characteristics of the output circuit C2 in this case. The vertical and horizontal axes are shown in FIG.
The vertical axis indicates the output voltage, and the horizontal axis indicates the load current. Output voltage V _o is, V
_{o In} the range of <V _BE (Q _a2 ), the current I
It becomes constant at _{sh ort.} V output voltage V _o increases
The range of _{BE (Q a2) ≦ V o} , the transistor Q _a2 becomes conductive, current flows I _a2 in accordance with the output voltage V _o in size.
And the output current output voltage V _o increases also continue to increase.
There is a fault in the load, when an excessive current flows, as described above, when V _o = V _a + V _BE of (Q _2), the maximum current limit value I _omax.

[0049] Such output voltage - since the load current characteristic, when the output voltage V _o is small, it is possible to reduce the current limit value I _omax, it is possible to reduce power consumption in the output device. Then, even if the output is short-circuited to the ground and the output voltage becomes 0 V, a certain amount of short-circuit current flows. As a result, a start-up failure can be prevented when the output circuit is started next time.

Next, the voltage / current change in the output circuit C2 will be described.
In the conversion circuit 7, the output voltage V_oIs V_o<V_BE(Q_a2) Range
, The short-circuit current I_shortIs a constant value, but the output power
Pressure V _o= 0, the short current I_shortThere is a size
Since the output circuit C3 shown in FIG.
Indicates the operation of the voltage / current conversion circuit 7a as the output voltage V_o=
0, the short-circuit current I_shortIt was made to become.

The basic circuit configuration of the output circuit C3 is shown in FIG.
3 is the same as the output circuit C2 shown in FIG. 3, and the same parts are denoted by the same reference numerals. However, in the voltage / current converting circuit 7, the collector of the transistor Q _a2 is connected resistors R _a1, but were those current I _a2 flowing through the transistor Q _a2 is controlled by the magnitude of the output voltage V _o, 15 In the voltage / current conversion circuit 7a, a mirror current with respect to the current _Ia2 flowing through the transistor _Qa2 flows.

A current mirror circuit is formed by PNP transistors Q _a3 and Q _a4 whose emitters are connected to the power supply 11, and the mirror ratio is set to 1: 1. By changing the mirror ratio, the detection sensitivity can be changed. The collector of the transistor Q _a3 is connected to the collector of the transistor Q _a2. On the other hand, the collector of the transistor _Qa4 is NP
The resistor R _a2 is connected to the collector of the N-transistor Q _{a5 and} the emitter of the transistor Q _a5 . The output terminals are connected to resistors _Ra3 and _Ra4 , and output voltage V
_o can be detected. The detected voltage is compared with the voltage across the resistor _Ra2 by the differential amplifier AMP, and the conduction of the transistor _Qa5 is controlled by the comparison output of the differential amplifier AMP.

The voltage / current conversion circuit 7a operates according to the voltage of FIG.
/ Current conversion circuit 7 differs from output voltage V_oIs 0 ≦ V_oof
Is to work in a range. Output circuit C3 shown in FIG.
Voltage / current conversion with reference to the output voltage-load current characteristics of
The operation of the circuit 7a will be described. Normally, the output voltage V_oIs before
As mentioned, V_o= V_a+ V_BE(Q_Two). Transistor Q_a1And transistor Q_a2And
Transistor Q_a3And transistor Q_a4Mirror ratio of 1:
1, the output current I of the voltage / current conversion circuit 7a is_a2
Is I_a2= V_o× R_a4/ (R_a3+ R_a4) / R_a2 Becomes Then, the current I_aIs I_a1= (V_b-V_BE(Q_Three)) / R_a1 Then I_a= I_a1+ I_a2 = (V_b-V_BE(Q_Three)) / R_a1 + V_o× R_a4/ (R_a3+ R_a4) / R_a2 Becomes Here, the voltage source 13 is set to a constant voltage V_bIf you set
Current I flowing through source 14 _a1Is constant. And tiger
Transistor Q_a2Current I flowing through_a2Is the output voltage V_oIn response to the
Change.

[0054] Then, the current limit value I _{omax is, I omax = N × I a} = N × (I a1 + I a2) = N × _{[(V b -V BE (Q 3} )) / R a1 + V o × R _a4 / ( _Ra3 + _Ra4 ) / _Ra2 ]. As a result, the short-circuit current I _{sh ort} that output flows when shorted to ground, when the V _o = 0, I _a2
= 0, so that I _short = N × I _a1 = N × [(V _b −V _BE (Q ₃ )) / R _a1 ]. When the output voltage V _o increases, the current limit value I
_omax also Yuki increased, when the V _o becomes _{V a + V BE (Q 2} ), the maximum.

According to the second embodiment described so far,
High-side driver circuit and series regulator
Output circuit with current limiting function applicable to circuits
Output voltage is short-circuited to ground
Even if the overcurrent is _omaxVoltage / electricity
By connecting the current conversion circuits 7 and 7a, the output voltage
V_oIs short-circuit current I_shortCan be secured. [Third Embodiment] In the output circuit C1 of the second embodiment,
Is provided with a voltage / current conversion circuit 7 so that the output voltage V_oIs small
The current limit value I_omaxTo reduce power loss
Although the output voltage is reduced to the power supply voltage
Therefore, the regulator circuit or high side
When applied to a switch circuit, the current limit value I_omaxIs
It will change according to the change of the source voltage. for that reason,
In some cases, the current limit function cannot be performed in the output circuit.
You.

[0056] Therefore, in the third embodiment, by applying a limiter function to the voltage / current conversion circuit, the output voltage V _o is also changed by a change in the power supply voltage, and to be able to hold a current limiting function . FIG. 17 shows an output circuit D1 according to the third embodiment. The basic circuit configuration of the output circuit D1 shown in FIG. 17 shows a case where it is applied to the same output circuit configuration as the output circuit B4 shown in FIG. 9, and the current mirror circuit 3, the voltage control circuit 4, the current limiting circuit 5, An output cut circuit 6 is provided. 17, the same parts as those in FIG. 9 are denoted by the same reference numerals.

Voltage / current conversion circuit 8 with limiter function
Is the voltage / current change used in the output circuit C1 shown in FIG.
The conversion circuit 7 is provided with a limiter function. That
The output voltage V_oIs the specified value
The current I of the current source 17 _a2Put a limit on
Caught. An output circuit which is a specific circuit configuration of the output circuit D1
The road D2 is shown in FIG. Basic components of the output circuit D2 itself
The physical circuit configuration is the same as that of the output circuit C2 in FIG.
is there.

Voltage / current conversion circuit 8 with limiter function
Is, NPN transistors Q _a1 and Q _a2, PNP transistor Q _a3, resistor R _a21 and R _a22, and is constituted by a voltage source V _c. Transistor Q _a1 and transistor Q _a2
With the above, a current mirror circuit is formed, and the transistor Q _a1 is formed.
_Is connected to the resistor Ra1 of the current source 13. This configuration is the same as that of the voltage / current conversion circuit 7 in FIG. 13 described above, and its mirror ratio is set to 1: 1.

Then, the transistor Q_a2The collector of
Resistance R_a21And resistance R_a22Is connected to the output terminal
You. This resistance R_a21And resistance R_a22Connection point and ground
And transistor Q_a3And a voltage source 1 at its base.
8 voltage V_cSupply. Limiter configured in this way
The operation of the voltage / current conversion circuit with function 8 will be described. here
And the output voltage V_oAnd the resistance R_a21And resistance R_a22
Is at V_c+ V_BE(Q_a3)
Transistor Q_a3Is turned off. This transistor Q_a3
Is not operating, the voltage / current conversion circuit described above is used.
It becomes the same as the road 7 and the current I_a2Is I_a2= (V_o-V_BE(Q_a2)) / (R_a21+ R_a22). Therefore, the output voltage V_oRises and the resistance R_a21When
Resistance R_a22Is at V_c+ V_BE(Q_a3)that's all
, The transistor Q_a3Turns on and operates.
Then, the transistor Q_a3Is the transistor Q_a2To
Current I flowing _a2Is the resistance R_a22Bypass from. This
This is the transistor Q_a2Current I flowing through_a2The Remi
That's it.

As described above, the current limit value of the current I _{a2 is} such that the potential at the connection point between the resistors Ra ₂₁ and Ra ₂₂ is V _c + V _BE (Q
from being clamped to _a3), the current limit value I _{a2 max} current I _{a2 is, I a2max = (V c +} V BE (Q a3) -V BE (Q a2)) / R a21 ≒ V c / R a21 Becomes At this time, the output current limiting value I _{omax outputs, I omax = N × I a} = N × (I a1 + I a2max) = N × _{[(V b -V BE (Q 3} )) / R a1 + V c / R _a21 ], and the detection voltage of the voltage / current conversion circuit 8 is V _c + V _BE
(Q _a3 ), the current I _a2 becomes the current limit value I
_Limited to _a2max .

The short-circuit current I _short flowing when the output is short-circuited to the ground is the same as the output voltage-load current characteristic shown in FIG. 14 in the case of the output circuit C2, as described above. [Fourth Embodiment] According to the voltage / current conversion circuit 7 in the second embodiment, even if the output is short-circuited to the ground and the output voltage becomes V _o = 0, a certain short-circuit current I
_{Made short} flow.

On the other hand, in the fourth embodiment, when the output drops below a predetermined voltage, it is determined that the output terminal is short-circuited to the ground, and the output current limit value _Iomax at that time is determined. A short-circuit control circuit is provided. FIG.
FIG. 9 shows a basic circuit configuration of an output circuit E1 according to the fourth embodiment. This basic circuit configuration is the same as that of output circuit B1 shown in FIG. 4, and the same parts in the figure are denoted by the same reference numerals.

In the output circuit E1, the short control circuit 9 is connected between the output terminal and the ground. Short control circuit 9, the current is controlled by the voltage V _b of the voltage source 13 I
a current source 19 diverts _a, detects that the output voltage V _o reaches a predetermined voltage, a switch SW ₂ to OFF at a predetermined voltage or less. When the output voltage V _o becomes equal to or lower than the predetermined voltage, when a current I _a is reduced to I _a1,
The current limit value _Iomax is reduced.

Specific circuit of output circuit E2 shown in FIG.
The configuration is shown in FIG. Here, the current source 14 shown in FIG.
The indicated resistance R_a1The case was shown. Short control circuit
9 is an NPN transistor Q_aAnd the resistance R_a2, R_x1
And R_x2It is composed of Transistor Q_aCollection of
Is a resistor R_a2Through the resistor R of the current source 14_a1Connected to
And the resistance R_x1And resistance R_x2Is connected between the output terminal and ground.
Has been continued. And the resistance R_x1And resistance R_x2Connection point
Potential of the transistor Q _aSupply to the base.

Normally, the output voltage V_oIs output to the output terminal.
The resistance R_x1And resistance R_x2Potential at connection point
The transistor Q_aIs conducting and the current I
_a2Is flowing. In this case, the current I_aIs I_a= I_a1+ I_a2 And the current limit value I at this time_omaxIs as described above
And I_omax= N × (I_a1+ I_a2). Here, the output voltage V_oDecreases, and V_o× R_x2/ (R_x1+ R_x2) <V_BE(Q_a), The transistor Q_aTurns off. so
Then, the current I_a2Will not flow. Therefore, at this time
Short current I_shortIs I_short= N × I_a1 It is. This state is shown in FIG.
Flow characteristics. Output voltage V_oIs V_BE(Q_a) × (R_x1
+ R_x2) / R_x2In the following cases, the short-circuit current I _short
And if it is greater than that, the current limit value I_omaxFlow.
Output voltage V_oOutput voltage V
_oIs smaller than the predetermined voltage, the short-circuit current I_shortTo
I let it flow.

[0066] In the output circuit E2 shown in FIG. 20, a short current I _short, the output voltage V _o is, V _BE (Q _a) ×
The flow is one step, depending on whether or not (R _x1 + R _x2 ) / R _x2 or less. This corresponding to a plurality of predetermined values of the output voltage V _o,
The output current _Io is changed in multiple steps, and the short-circuit current Io
An output circuit E3 in which _short flows are described. FIG. 22 shows a case where the output voltage of the output circuit E3 is detected in two stages.

The output circuit E3 shown in FIG. 22 shows a case where the output circuit E1 of FIG. 19 is applied to the series regulator circuit of FIG. The basic circuit configuration of the output circuit E3 is the same as that of the series regulator circuit B2, and the same parts are denoted by the same reference numerals. The current source 14 used was the resistor _Ra1 shown in FIG. The output circuit E3 is
The detection side of the short control circuit 9a is connected to the output terminal of the series regulator circuit B2,
a is connected to the resistor R _a1 of the current source 14.

The short control circuit 9a forms two current paths, one is composed of an NPN transistor _Qa2 and a resistor _Ra2 , and the other is composed of an NPN transistor _Qa3 and a resistor _Ra3 . . These current paths are connected to the resistor _Ra1 of the current source 14. Furthermore, a comparator for comparing a comparator CMP1 for comparing the output voltage V _o and the first voltage V _x1, the output voltage V _o and the second voltage V _x2 CMP2
And Controls transistors Q _a2 at the output of the comparator CMP1, and controls the transistor Q _a3 at the output of the comparator CMP2. Here, the first voltage V _x1 and the second voltage V _x2 are set to V _x1 <V _x2 .

Referring to FIG. 23 showing the output voltage-load current characteristics of output circuit E3, the operation of short control circuit 9a will be described. When the high output voltage V _o, the current I _a2
And I _a3 are flowing. The current limit value at this time is I _omax
It is. When the output voltage V _o is lowered, the comparator CMP2 senses a second voltage V _x2, to turn off the transistor Q _a3, not current flows I _a3. In this case, the current limit value is _Iomid . Then, the output voltage V
_{When o} further decreases, the comparator CMP1 detects the first voltage V _x1 and turns off the transistor Q _a2 . When the output voltage V _o is equal to or less than the first voltage V _x1, the output voltage V
_o even if not short-circuited to the ground, as the output voltage V _o those similar to the short-circuited to the ground, short current I
_{Made short} flow.

Note that the short control circuit 9a uses the comparators CMP1 and CMP2 to
Since so as to compare the output voltage V _o at step, when the switching of these comparators may cause chattering. In order to prevent the chattering, the comparator may have a hysteresis characteristic.

[0071] In addition, a set of current sources and comparators preparing a plurality may be controlled to vary the current I _a in multiple stages. [Fifth Embodiment] In the output circuits shown in the second to fourth embodiments, the output voltage V _o is set when the circuit starts up.
Is increased from 0 V, so that when the power supply of the circuit is turned on, the output current limit value at that moment is in a low state (I _short ). When the output circuit is applied to a series regulator circuit, a large-capacity capacitor is usually connected to the output terminal for stabilizing the output voltage. Therefore, if the current limit value is small, there is a problem that it takes time for the output to rise.

Therefore, in the fifth embodiment, the current limiting value is increased for a predetermined period after the power supply voltage has risen, so that the rising speed of the output voltage when the power supply starts up is increased, thereby solving the above problem. . FIG. 24 shows a basic circuit configuration of an output circuit F1 according to the fifth embodiment. The circuit configuration of the output circuit F1 is the same as that of the output circuit E1 shown in FIG. 19, and the same parts are denoted by the same reference numerals. Further, the output circuit F1 is applied to the output circuit E1 shown in FIG. 19 in the series regulator circuit, a capacitor C ₁ of a large capacity is connected to the output terminal.

The output terminal of the output circuit F1 is short-circuited.
The control circuit 9 is connected. Output voltage V_oAccording to the size of
The switch SW in the short control circuit 9_TwoNo
By controlling turn-off, the current I_a2
Is turned on and off. On the other hand, the output circuit F1
The power supply 11 has a power supply voltage detection which is a feature of the fifth embodiment.
The control circuit 20 is connected. Power supply voltage detection control circuit
Reference numeral 20 includes a power supply voltage detection circuit 21 and a timer circuit.
The magnitude of the power supply voltage Vcc of the power supply 11 by the power supply voltage detection circuit 21
Is detected. Then, the timer circuit 22 activates the power supply 11.
At the time of hoisting, the detection circuit 21 detects a predetermined value.
Switch SW after fixed time_ThreeTurn on. This switch
SW_ThreeIs the current I of the current source 19_a2Control of conduction and non-conduction of
Switch SW_TwoConnected in parallel with
You. This switch SW_ThreeControl from the time the power is turned on
By turning on for a predetermined time, the current I_aTo I_a1+
I _a2To be larger. After a predetermined time, the switch
SW_ThreeIs turned off and the current I_aTo I_a1To be smaller. So
Therefore, the current is limited within a predetermined time after the power is turned on.
Value is I_omaxBecomes capacitor C₁Charge the battery faster
Can be.

FIG. 25 shows a specific circuit configuration of the output circuit F1 as an output circuit F2. The short-circuit control circuit 9 has the same circuit configuration as that of the short-circuit control circuit 9 in the output circuit E2 in FIG. 20, and also has the same operation. Also, the power supply voltage detection circuit 21 of the power supply voltage detection control circuit 20
_Are the NPN transistor Q _y1 , the resistors R _y1 , R _y2 and R _y3
, And the resistor R _y1 is connected to the power supply 11. The potential at the connection point of the resistors R _y2 and the resistor R _y3 is supplied to the base of the transistor Q _y1, controls the conduction of transistor Q _y1 by the height of the potential.

Further, the power supply voltage detection control circuit 20
The circuit 22 includes a capacitor C_yAnd the resistance R_y2And resistance R
_y3It is formed by. Resistance R_y2And resistance R_y3Potential at connection point
Is a predetermined time after the power is turned on._y1
So that the capacitor C is turned on._y, Resistance R_y2And
Anti-R_y3Set the time constant according to. Power supply voltage detection control
Switch SW in circuit 20_ThreeIs NPN Transis
TA Q _y2And its base is transistor Q_y1Collection of
Connected to the Transistor Q_y2The collector of
Transistor Q of short control circuit 9_xWith the collector
The resistance R of the current source 19_a2It is connected to the. Tran
Jista Q_y2Is the transistor Q_y1Is on when is off
You. Therefore, the transistor Q_y1From when the power is turned on
It turns on after a predetermined time,
Q_y2Is turned off and the current I_a2And the current I
_aCurrent I_a1Flow.

The operation of the output circuit F2 thus configured will be described with reference to the timing charts of FIGS. 26 and 27. The timing chart of FIG.
2 shows a case where the power supply is started in a normal state where there is no abnormality in the load. In FIG. 26, (a) is the ON state of the power supply voltage Vcc of the power supply 11, the (b) is the voltage across V _cy of the capacitor C _y of the timer circuit 22, (c) the transistor Q _y1
Of the on-off, the (d) of the on-off of the transistor Q _y2, (e) is a start-up state of the output voltage V _o, (f) is turned on and off of the transistor Q _x of short control circuit 9 and represents (g), respectively the change of the current I _a.

[0077] and here, it has started up the output circuit F2 to time t _1. Be a power supply 11 rises immediately at time t _1, capacitor C ₁ connected to the output terminal for a large capacity, its voltage V _o will rise slowly as shown in (e). On the other hand, when the power supply 11 rises at time t ₁ as shown in FIG.
_y2 turns on immediately. However, the voltage across V _cy of the capacitor C _y of the timer circuit 22, since we rise with a predetermined time constant as shown in (b), the transistor Q _y1 is off. Therefore, it flows I _a1 + I _a2 as the current I _a at time t ₁ as shown in (g).

As shown in (e), the output voltage V_oRises
When a predetermined voltage is reached, time t_TwoIn (f),
The transistor Q of the short control circuit 9 is_xBut
However, at this time, the transistor Q_y2But
The current I _aAffect the size of
Without, I_a1+ I_a2Remains. Output voltage V_oGasa
Then, as shown in (b), the timer circuit 2
2 capacitor C_yVoltage V_cyWill also be higher,
Interval t_ThreeIn the transistor Q_y1Turn off to on
You. Thereby, the transistor Q_y2From on to off
You. However, time t_ThreeAt the time of the transistor Q
_xIs on, the current I_aDoes not affect_a1+
I_a2Remains.

[0079] In the case without the supply voltage detection control circuit 20, the transistor Q _x is because not turned ON, I _a1 only flows as a current I _a to the time t _2. According to the fifth embodiment, since the current of I _a1 + I _a2 can flow from the time of power-on, the speed of rising of the output voltage at the time of power-on can be increased. Next, the operation of the output circuit F2 in the case where the output is short-circuited or the load has failed will be described with reference to the timing chart of FIG. (A) through
(g) shows a chart similar to (a) to (g) of FIG.

[0080] and here, it has started up the output circuit F2 to time t _1. It is a power supply 11 rises immediately at time t _1, when such an output of the output terminal is short-circuited, the voltage V _o is not rise as shown in (e), remain 0V. On the other hand, when the power supply 11 rises at time t ₁ as shown in FIG.
_y2 turns on immediately. However, the voltage across V _cy of the capacitor C _y of the timer circuit 22, since we rise with a predetermined time constant as shown in (b), the transistor Q _y1 is off. Therefore, it flows I _a1 + I _a2 as the current I _a at time t ₁ as shown in (g).

[0081] The output voltage V _o, as shown in (e) is 0V
Since remains, the transistor Q _x short control circuit 9, as shown in (f) which is still off, because it has already transistor Q _y2 is turned on at this time, the current I _a size The value remains at I _a1 + I _a2 . Although the output voltage V _o is still 0V, power supply 11 is voltage V
because it is providing cc, as shown in (b), the voltage across V _cy of the capacitor C _y of the timer circuit 22 also increases.
Then, at time t _3, since the turning on transistor Q _y1 from OFF, the transistor Q _y2 is turned off from on. However, since also the transistor Q _x short control circuit 9 remains off, at time t _3, no current flows through the current source 19. Thus, the current I _a
Will decrease from the magnitude of I _a1 + I _{a2 to} the magnitude of I _a1 .

[0082] When such an output is short-circuited, when not provided with the power supply voltage detection control circuit 20, will continue to flow a current of I _a1 + I _a2 as the current I _a, the current limit is high state (I _omax ), according to the fifth embodiment, even if a current of I _a1 + I _a2 flows from the time of power-on, the timer circuit 22 operates to _reduce the magnitude of the current I _a to I _a1 + I a. _a2 can be reduced to _Ia1 , and the current limit value can be suppressed to a low state ( _Ishort ).

Although the above description has been given of the case where the output circuit is applied to a series regulator circuit, the output circuit can be applied to a high-side switch circuit. Sixth Embodiment In the output circuits F1 and F2 according to the fifth embodiment shown in FIGS. 24 and 25, the rise of the power supply voltage of the power supply 11 is detected, and I _a1 +
As flown a current of I _a2, but was to quickly rise of the output voltage, in the sixth embodiment, in the case of application to a series regulator circuit and the high-side switch circuit having an output cut circuit, This is to speed up the rise of the output voltage.

An output circuit G1 according to a sixth embodiment applied to a regulator circuit having an output cut circuit is shown in FIG.
FIG. The basic circuit configuration of the output circuit G1 is the same as that of the output circuit F1 shown in FIG. 24. However, in the output circuit F1, the power supply voltage detection control circuit 20 is connected to the power supply 11 and While the timer circuit is operated, the output circuit G1 is connected to an on-input detection control circuit 23 having an output cut circuit, and detects an on-input input to the output cut circuit 6. It is. In FIG. 28, the same parts as those in FIG. 24 are denoted by the same reference numerals.

The output control circuit 9 is connected to the output terminal of the output circuit G1. In the steady state with no abnormality in the load, the I _a1 + I _a2 as the current I _a flowing, current limit has a I _omax. There is a problem such as the load, the output voltage V _o is 0, to stop the current I _a2 of the current source 9 to turn off the switch SW _2, I _a1 to flow as current I _a, the current limit value I _short It is supposed to.

[0086] Between the emitter and the collector of the transistor Q _1a to form a current mirror circuit 3 of the output circuit G1, the switch SW ₁ of the output cut circuit 6 is connected. The on-off control of the switch SW ₁ at the input voltage V _i. When the switch SW ₁ is turned on, the operation of the current mirror circuit 3 is stopped, the output current I _o from the output terminal of the output circuit G1 does not flow.

On the other hand, an on-input detection control circuit 23 is connected to the input of the output cut circuit 6. This on the input detection value control circuit 23 includes an ON input detection circuit 24 for detecting the H · L of the input voltage V _i, comprise a timer circuit 25 for the on-input detection circuit 24 is operated by the detection of the input voltage V _i I have. Then, the switch SW ₃ is, similar to the switch SW ₂ of the short control circuit 9 is connected to a current source 19, the timer circuit 25 controls the switch SW _3.

The ON input detection circuit 24 detects the input voltage V_iBut
When detecting the change from H to L, the timer circuit 25
The operation of is started. At this time, the switch SW_ThreeIs on
The current I of the current source 19_a2The current I_a
As I_a1+ I_a2Flows. Then a predetermined time elapses
And the timer circuit 25 includes a switch SW_ThreeOff from
You. Then, the current I of the current source 19 is_a2Stop flowing
Therefore, the current I_aAs I _a1Flows. Here, turn on
The operation of the force detection control circuit 23 ends.

FIG. 29 shows a specific circuit configuration of the output circuit G1 shown in FIG. 28 as an output circuit G2 applied to a series regulator circuit. The basic part of the output circuit G2 is the same as the specific circuit configuration of the output circuit F2 shown in FIG. 25, and the same parts are denoted by the same reference numerals. FIG.
In the output circuit F2 shown in FIG. 29, the power supply voltage detection control circuit 20 is connected to the power supply 11, and in the output circuit G2 of FIG. 29, the output cut circuit 6 is connected to the current mirror circuit 3, The ON input detection control circuit 23 is connected to the input of the circuit 6.

The output cut circuit 6 includes PNP transistors Q ₄ and Q ₅ and resistors R ₆₁ and R _62. The emitter and the collector of the transistor Q ₄ are connected to the emitter of the transistor Q ₁ a forming the current mirror circuit 3. Each is connected to a collector. The base of transistor Q ₄ are connected to the collector of the transistor Q _5, further the base of the transistor Q _5, the resistor R ₆₁ and the resistor R ₆₂
Connected to the connection point. And the transistor Q _5
Has an input voltage V input through a resistor R61.
_i is supplied.

[0091] Here, when the input voltage V _i is L, the transistor Q ₅ is turned on, is the base potential of the transistor Q ₄ is a power supply voltage Vcc, the transistor Q ₄ are turned off. In this case, the current mirror circuit 3 is operating, and supplies an output current I _o to an output terminal. On the other hand, when the input voltage V _i is H, the transistor Q ₅ is to become off, and the base potential of the transistor Q ₄ is at ground potential, the transistor Q ₄ are turned on. At this time, the operation of the current mirror circuit 3 is stopped, and the output current _Io is not supplied to the output terminal.

ON input detection of ON input detection control circuit 23
The circuit 24 includes a PNP transistor Q ₆, Resistance R₆₁And R
₆₂And the transistor Q₆The base of the resistor
R₆₁And R₆₂And the resistor R₆₁Input via
Voltage V_iIs supplied. Input voltage V_iIf L is
Transistor Q₆Turns on, and if H, turns off
So, transistor Q₆Input voltage V_i
Is detected.

Switch SW of ON input detection control circuit 23
₃ is an NPN transistor Q _y1 and Q _y2 , a resistor R _y1 ,
Is composed of R _y2 and R _y3, the collector of the transistor Q _y1 is connected to the current source 19, its base is connected to the collector of the transistor Q _y2. The base of the transistor Q _y2 is connected to the resistor R _y2 to the connection point of the resistors R _y3, the resistor R _y1, the collector of the transistor Q ₆ is connected.

[0094] of the transistor Q ₆ is an input voltage V _i H · L
The transistor Q _{y1 is} turned on / off in response to
Can be turned on and off. Timer circuit 25 on the input detection control circuit 23, a capacitor C _y and the resistance R _y2 and R _y3. The potential at the connection point between the resistor R _y2 and the resistor R _y3 to which the base of the transistor Q _y2 is connected rises with a predetermined time constant from the time when the transistor Q ₆ is turned on, and turns on the transistor Q _y2 for a predetermined time. I do. At this time, the transistor Q _y1 is turned off,
To not shed the current I _a2 from the current source 19.

Operation of output circuit G2 configured as described above
With reference to the timing charts shown in FIGS. 30 and 31.
It will be described in the light of the above. The timing chart of FIG.
Circuit G2 is powered up in normal condition with no load abnormalities.
Is shown. In FIG. 30, (a) is the output
V of the input voltage to the reset circuit 6_i(B)
Transistor Q_FiveAnd transistor Q ₆On / off
(c) is the capacitor C of the timer circuit 22._yVoltage V_cy
And (d) shows the transistor Q_y1On and off, and (e)
Transistor Q_y2(F) is the output voltage V_oof
(G) shows the transient state of the short control circuit 9.
Star Q_xAnd (h) is the current I_aStrange
, Respectively.

[0096] Here, to launch an output circuit G2 to time t _1, to L input voltage V _i to the output cut circuit 6 from H. Flows an output current I _o from the current mirror circuit 3, a capacitor C ₁ connected to the output terminal for a large capacity, its voltage V _o will rise slowly as shown in (f). On the other hand, the transistor Q _y2 becomes immediately turned on at time t ₁ as shown in (e). However, since the voltage across V _cy of the capacitor C _y of the timer circuit 22, will stand up at a predetermined time constant as shown (c), the
Transistor _Qy1 is off. Therefore, (h)
I _a1 as the current I _a at time t ₁ as shown in
+ I _a2 flows.

As shown in (f), the output voltage V_oRises
When a predetermined voltage is reached, time t_TwoIn (g)
The transistor Q of the short control circuit 9 is_xBut
However, at this time, the transistor Q_y2But
The current I _aAffect the size of
Without, I_a1+ I_a2Remains. Output voltage V_oGasa
Then, as shown in (c), the timer circuit 2
2 capacitor C_yVoltage V_cyWill also be higher,
Interval t_ThreeIn the transistor Q_y1From off to on
You. Thereby, the transistor Q_y2From on to off
You. However, time t_ThreeAt the time of the transistor Q
_xIs on, the current I_aDoes not affect_a1+
I_a2Remains.

[0098] If not provided with an on input sense control circuit 23, and since they are not time t ₂ until the transistor Q _x is on and, I _a1 only flows as a current I _a. According to the sixth embodiment, since the current of I _a1 + I _a2 can flow from the start of the output circuit G2 with the output cut circuit 6 turned off, the rising speed of the output voltage at the start of the output circuit can be reduced. Can be faster.

Next, the operation of the output circuit G2 in the case where the output is short-circuited or the load has failed will be described with reference to the timing chart of FIG. (A) to (h) in the same drawing show charts similar to (a) to (h) in FIG. Output circuit G Here, the time t ₁
Suppose that the start of 2 starts. An output cut circuit 6 turns off as the output circuit G2 rises immediately at time t _1, when such an output of the output terminal is short-circuited, the voltage V _o, as shown in (f) It does not rise and remains at 0V. On the other hand, when the output circuit G2 rises at time t ₁ as shown in FIG.
_y2 turns on immediately. However, since the voltage V _cy across the capacitor C _y of the timer circuit 22 rises with a predetermined time constant as shown in (c), the transistor Q _y1 is off. Therefore, flows I _a1 + I _a2 as the current I _a at time t ₁ as shown in (h).

[0100] The output voltage V _o, as shown in (f) is 0V
Since remains, the transistor Q _x short control circuit 9, as shown in (g) which is still off, because it has already transistor Q _y2 is turned on at this time, the current I _a size The value remains at I _a1 + I _a2 . Although the output voltage V _o is still 0V, power supply 11 is voltage V
because it is providing cc, as shown (c), the voltage across V _cy of the capacitor C _y of the timer circuit 22 also increases.
Then, at time t _3, since the turning on transistor Q _y1 from OFF, the transistor Q _y2 is turned off from on. However, since also the transistor Q _x short control circuit 9 remains off, at time t _3, no current flows through the current source 19. Thus, the current I _a
Will decrease from the magnitude of I _a1 + I _{a2 to} the magnitude of I _a1 .

[0102] When such an output is short-circuited, if not provided with an on input sense control circuit 23, will continue to flow a current of I _a1 + I _a2 as the current I _a, the current limit is high state (I _omax) and turned to cause, but according to the sixth embodiment, even when the current of I _a1 + I _a2 flows from when the power supply is turned on, by the operation of the timer circuit 22, the magnitude of the current I _a I _a1 + I _a2 can be reduced to _Ia1 , and the current limit value can be suppressed to a low state ( _Ishort ).

In the above description, the case where the output circuit is applied to a series regulator circuit has been described. However, this output circuit can be applied to a high-side switch circuit.

[0103]

As described above, if the output circuit according to the embodiment of the present invention is applied to a series regulator circuit, a high-side driver circuit, or the like, an overcurrent state due to a short-circuit to the ground of the output terminal, an abnormal load, etc. In this case, the circuit element can be protected from overcurrent because it has a current limiting function capable of lowering the current limiting value.

[Brief description of the drawings]

FIG. 1 is a diagram of a high-side driver circuit with a current limiting function according to a conventional example.

FIG. 2 is a diagram of a high-side driver circuit with a current limiting function according to a conventional example.

FIG. 3 is a diagram of a series regulator circuit with a current limiting function according to a conventional example.

FIG. 4 is a diagram of an output circuit with a current limiting function according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram of a current source used in the embodiment of the present invention.

FIG. 6 is a diagram of a series regulator circuit with a current limiting function according to the first embodiment of the present invention.

FIG. 7 is a diagram of a high-side driver circuit with a current limiting function according to the first embodiment of the present invention.

8 is a diagram showing a specific circuit configuration of a high-side driver circuit with a current limiting function in FIG. 7;

FIG. 9 is a diagram of a high-side driver circuit with a current limiting function having an output cut circuit according to the first embodiment of the present invention.

10 is a diagram showing a specific circuit configuration of a high-side driver circuit with a current limiting function in FIG. 9;

FIG. 11 is a diagram showing output voltage-load current characteristics of the output circuit according to the first embodiment of the present invention.

FIG. 12 is a diagram of a high-side driver circuit with a current limiting function according to a second embodiment of the present invention.

13 is a diagram showing a specific circuit configuration of a high-side driver circuit with a current limiting function in FIG.

FIG. 14 is a diagram showing output voltage-load current characteristics of the output circuit according to the second embodiment of the present invention.

FIG. 15 is a diagram showing a specific circuit configuration of another high-side driver circuit with a current limiting function according to the second embodiment of the present invention.

FIG. 16 is a diagram showing output voltage-load current characteristics of another output circuit according to the second embodiment of the present invention.

FIG. 17 is a diagram of a high-side driver circuit with a current limiting function having an output cut circuit according to a third embodiment of the present invention.

18 is a diagram showing a specific circuit configuration of a high-side driver circuit with a current limiting function in FIG.

FIG. 19 is a diagram of a high-side driver circuit with a current limiting function according to a fourth embodiment of the present invention.

20 is a diagram showing a specific circuit configuration of a high-side driver circuit with a current limiting function in FIG. 19;

FIG. 21 is a diagram showing output voltage-load current characteristics of an output circuit according to a fourth embodiment of the present invention.

FIG. 22 is a diagram showing a specific circuit configuration of a series regulator circuit with a current limiting function according to a fourth embodiment of the present invention.

FIG. 23 is a diagram showing output voltage-load current characteristics of a series regulator circuit according to a fourth embodiment of the present invention.

FIG. 24 is a diagram of a series regulator circuit with a current limiting function according to a fifth embodiment of the present invention.

25 is a diagram showing a specific circuit configuration of a series regulator circuit with a current limiting function in FIG. 24.

FIG. 26 is a timing chart showing an operation of the output circuit according to the fifth embodiment in a normal state.

FIG. 27 is a timing chart showing an operation of the output circuit according to the fifth embodiment in an abnormal state.

FIG. 28 is a diagram of a series regulator circuit with a current limiting function having an output cut circuit according to a sixth embodiment of the present invention.

29 is a diagram showing a specific circuit configuration of a series regulator circuit with a current limiting function in FIG. 28.

FIG. 30 is a timing chart showing an operation of the output circuit according to the sixth embodiment in a normal state.

FIG. 31 is a timing chart showing an operation of the output circuit according to the sixth embodiment in an abnormal state.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 3 ... Current mirror circuit 4 ... Voltage control circuit 5 ... Current control circuit 6 ... Output cut circuit 7, 7a ... Voltage / current conversion circuit 8 ... Voltage / current conversion circuit with limiter function 9 ... Short control circuit 11 ... Power supply 12, 13 , 15, 18 ... voltage source 14, 16, 17, 19 ... current source 20 ... power supply voltage detection control circuit 21 ... power supply voltage detection circuit 22 ... timer circuit 23 ... ON input detection control circuit 24 ... ON input detection circuit _Q1a , _{Q 1b, Q 2, Q 3} ... transistor _{R a, R a1, R a2} ... resistance C _1, C _y ... capacitor SW1, SW1, SW2 ... switch _{I 1, I 2, I a} ... current V _a, V _b, V _cc ... voltage

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H420 NA17 NB02 NB24 NB26 NB36 NC03 NC26 NE15 5J055 AX26 AX64 BX18 DX03 EY01 EY17 EZ16 FX04 FX05 FX19 GX01 GX02 5J091 AA01 CA57 FA01 FA04 HA08 HA25 HA29 KA07 KA07 KA07 KA07 KA00 MA21 TA02 TA06

Claims (13)

[Claims] 1. An output circuit with a current limiting function having a current mirror circuit, a current control circuit, and a voltage control circuit, wherein the current mirror circuit has a first mirror having a mirror ratio of 1: N based on a current from a power supply. Forming a second current with the current, wherein the first current is supplied from the current control circuit;
Supplying the second current to an output terminal, wherein the current control circuit has a first current control element and a first current source, and controls the first current flowing through the first current source by the first current control element. An output circuit with a current limiting function, wherein the voltage control circuit is connected to the output terminal and controls an output voltage. 2. The output circuit with a current limiting function according to claim 1, wherein said output circuit is a high-side driver circuit. 3. The output circuit according to claim 1, wherein the output circuit is a series regulator circuit. 4. The voltage control circuit includes a voltage control element connected between the output terminal and the first current source, the voltage control element being driven by the first voltage source, and the output voltage with respect to the first voltage source. 2. The output circuit with a current limiting function according to claim 1, wherein the first current flowing through the current source can be controlled by changing a driving state of the voltage control element according to the state. 5. The current control circuit according to claim 1, wherein the current control circuit has an output cut circuit that cuts off the current of the first current source, and the operation of the current mirror circuit is stopped by the operation of the output cut circuit. Output circuit with current limit function. 6. The current limiting function according to claim 1, wherein the current mirror circuit has an output cut circuit for stopping the first current, and the operation of the current mirror circuit is stopped by the operation of the output cut circuit. With output circuit. 7. A voltage / current conversion circuit including a second current source that outputs a current that varies according to the output voltage, wherein the second current source is connected in parallel to the first current source, The output circuit with a current limiting function according to claim 1, which controls the first current. 8. The output circuit with a current limiting function according to claim 7, wherein the voltage / current conversion circuit cuts off the current of the second current source when the output voltage is equal to or lower than a predetermined voltage. 9. The voltage / current conversion circuit has a limiter circuit that clamps the detected voltage when the output voltage reaches a predetermined voltage, and the voltage / current conversion circuit detects the output voltage according to the detected voltage. The output circuit with a current limiting function according to claim 7, which controls a current. 10. A short current control circuit including a third current source connected in parallel to the first current source, and a second current control element for controlling the third current source, wherein the short control circuit comprises: Outputting a current of the third current source in accordance with the output voltage, and when the output voltage drops to a predetermined voltage,
2. The output circuit with a current limiting function according to claim 1, wherein the current of the third current source is cut off by a current control element. 11. The third current source includes a plurality of current sources connected in parallel to the first current source, respectively, and the short control circuit controls a current of the plurality of current sources in accordance with the output voltage. 11. The output circuit with a current limiting function according to claim 10, wherein when the output voltage decreases, the current of each of the plurality of current sources is sequentially cut off in accordance with the set plurality of predetermined voltages. 12. 12. A power supply voltage detection control circuit including a power supply voltage detection circuit, a timer circuit, and a third current control element, wherein the power supply voltage detection circuit detects a rise of the power supply voltage,
The timer circuit which is started to drive at the time of the rise controls the third current control element after a lapse of a predetermined time, and
The output circuit with a current limiting function according to claim 11, wherein the current of the current source is cut off. 13. An on-input detecting circuit connected to the current mirror circuit for stopping the first current in response to an input voltage, detecting an input voltage, a timer circuit starting driving from the detection time, A fourth current control element for controlling the third current source by the timer circuit, wherein the timer circuit controls the fourth current control element after a lapse of a predetermined time from the detection point in time to control the third current source. The output circuit with a current limiting function according to claim 11, wherein the current is cut off.